The present invention relates to a novel structure for a golf ball, and more particularly to a golf ball with a moisture vapor barrier layer.
Solid core golf balls are well known in the art. Typically, the core is made from polybutadiene rubber material, which provides the primary source of resiliency for the golf ball. U.S. Pat. Nos. 3,241,834 and 3,313,545 disclose the early work in polybutadiene chemistry. It is also known in the art that increasing the cross-link density of polybutadiene can increase the resiliency of the core. The core is typically protected by a cover from repeated impacts from the golf clubs. The golf ball may comprise additional layers, which can be an outer core or an inner cover layer. One or more of these additional layers may be a wound layer of stretched elastic windings to increase the ball""s resiliency.
A known drawback of polybutadiene cores cross-linked with peroxide and/or zinc diacrylate is that this material is adversely affected by moisture. Water moisture vapor reduces the resiliency of the cores and degrades its properties. A polybutadiene core will absorb water and loose its resilience. Thus, these cores must be covered quickly to maintain optimum ball properties. The cover is typically made from ionomer resins, balata, and urethane, among other materials. The ionomer covers, particularly the harder ionomers, offer some protection against the penetration of water vapor. However, it is more difficult to control or impart spin to balls with hard covers. Conventional urethane covers, on the other hand, while providing better ball control, offer less resistance to water vapor than ionomer covers.
Prolonged exposure to high humidity and elevated temperature may be sufficient to allow water vapor to invade the cores of some commercially available golf balls. For example at 110xc2x0 F. and 90% humidity for a sixty day period, significant amounts of moisture enter the cores and reduce the initial velocity of the balls by 1.8 ft/s to 4.0 ft/s or greater. The change in compression may vary from 5 PGA to about 10 PGA or greater. The absorbed water vapor also reduces the coefficient of restitution (COR) of the ball.
Several prior patents have addressed the water vapor absorption problem. U.S. Pat. No. 5,820,488 discloses a golf ball with a solid inner core, an outer core and a water vapor barrier layer disposed therebetween. The water vapor barrier layer preferably has a water vapor transmission rate lower than that of the cover layer. The water vapor barrier layer can be a polyvinylidene chloride (PVDC) layer. It can also be formed by an in situ reaction between a barrier-forming material and the outer surface of the core. Alternatively, the water vapor barrier layer can be a vermiculite layer. U.S. Pat. Nos. 5,885,172 and 6,132,324 disclose, among other things, a golf ball with a polybutadiene or wound core with an ionomer resin inner cover and a relatively soft outer cover. The hard ionomer inner cover offers some resistance to water vapor penetration and the soft outer cover provides the desirable ball control. It is also desirable to minimize the water barrier layer such that other properties of the ball are unaffected. Additionally, U.S. Pat. No. 5,875,891 discloses an impermeable packaging for golf balls. The impermeable packaging acts as a moisture barrier limiting moisture absorption by golf balls during storage.
However, there remains a need for other golf balls with an improved water vapor barrier layer and improved methods for applying a water vapor barrier layer on to the core of the golf ball.
The present invention is directed to a golf ball comprising a thin film of moisture vapor barrier with a moisture vapor transmission rate preferably lower than that of the cover and more preferably less than or equal to that of an ionomer resin. The moisture vapor barrier may also comprise nano particles, flaked-metals, such as mica, iron oxide and aluminum, or ceramic particles disposed in the film to resist the transmission of moisture into the core.
The present invention is also directed to a golf ball comprising a soft, high specific gravity layer. Preferably, this layer also has a low moisture vapor transmission rate to decrease the amount of moisture penetrating into the core of the golf ball. The high specific gravity layer advantageously contributes to a high moment of inertia, low spin ball.
The present invention is also directed to a golf ball comprising a moisture vapor barrier, which can be a multi-layer thermoplastic film, a blend comprising ionomers, polyvinyl alcohol copolymer and polyamides, or a dispersion of acid salts of polyetheramines.
In accordance to another aspect of the invention, the moisture vapor barrier can be an intermediate layer, an inner cover layer, an outer core layer, a core coating or an outer cover coating.
The present invention is also directed to a golf ball having a moisture vapor barrier layer with a solid core and intermediate wound layer(s). The moisture vapor barrier layer is preferably applied to a wound layer and penetrates into the interstitial spaces in the wound layer(s) to minimize the transmission of moisture vapor to the intermediate wound layer(s) and to the core. Each of the wound layers is preferably made up of a material that is chemically, mechanically and physically different than an adjacent wound layer.
The present invention is also directed to a golf ball having a thin moisture vapor barrier layer with a thin thermoset urethane cover. Alternatively, the cover layer may be a relatively thick layer. The thick cover allows more spin, feel, control and playability for greenside play.
The present invention is also directed to a method of making a golf ball with a moisture vapor barrier layer. In accordance to one aspect of the present invention, any layer of the golf ball can be made by a single component casting method. Preferably, this single component casting method utilizes uretdione or isocyanate blocked materials, and is, therefore, stable at a predetermined low temperature. However, this material becomes deblocked at a predetermined elevated temperature and reacts to form the moisture vapor barrier layer or other components of the ball.
In accordance to another aspect of the invention, the thin moisture vapor barrier layer can also be manufactured by a two-component castable system. Preferably, two distinct castable components are mixed and react with each other prior to casting to form the moisture vapor barrier layer. The moisture vapor barrier layer may also be formed by spraying, dipping, preformed semi-cured shells, compression molding of sheet stock, injection molding, reaction injection molding or other methods.